FIGS. 1 and 2 depict a known printing system which includes a coated fuser system substrate, i.e., a coated fuser roller. Referring to FIG. 1, in a typical electrostatographic reproducing apparatus, a light image of an original image to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles, which are commonly referred to as toner. Specifically, photoreceptor 10 is charged on its surface by means of a charger 12 to which a voltage has been supplied from power supply 14. Photoreceptor 10 is then exposed to light from an optical system or an image input apparatus 16, such as a laser and light emitting diode, to form an electrostatic latent image thereon. Generally, the electrostatic latent image is developed by bringing a developer mixture from developer station 18 into contact therewith. Development can be effected by use of a magnetic brush, powder cloud, or other known development process. A dry developer mixture usually comprises carrier granules having toner particles adhering triboelectrically thereto. Toner particles are attracted from the carrier granules to the latent image forming a toner powder image thereon. Alternatively, a liquid developer material may be employed, which includes a liquid carrier having toner particles dispersed therein. The liquid developer material is advanced into contact with the electrostatic latent image and the toner particles are deposited thereon in image configuration.
After the toner particles have been deposited on the photoconductive surface, in image configuration, they are transferred to copy sheet 20 by transfer means 22, which can be pressure transfer or electrostatic transfer. Alternatively, the developed image can be transferred to an intermediate transfer member, or bias transfer member, and subsequently transferred to a copy sheet. Examples of copy substrates include paper, transparency material such as polyester, polycarbonate, or the like, cloth, wood, or any other desired material upon which the finished image will be situated.
After the transfer of the developed image is completed, copy sheet 20 advances to fusing station 24, depicted in FIG. 1 as fuser roll 26 and pressure roll 28, although any other fusing components such as a fuser belt in contact with a pressure roll, a fuser roll in contact with pressure belt, and the like, are suitable for use with this apparatus, wherein the developed image is fused to copy sheet 20 by passing copy sheet 20 between fusing roll 26 and pressure roll 28, thereby forming a permanent image. Alternatively, transfer and fusing can be effected by a transfix application.
Photoreceptor 10, subsequent to transfer, advances to cleaning station 30, wherein any toner left on photoreceptor 10 is cleaned therefrom by use of a blade, as shown in FIG. 1, a brush, or other cleaning apparatus.
FIG. 2 is an enlarged schematic view of an embodiment of a fuser member, where fuser roll 26 comprises elastomer surface 32 upon base member 34, e.g., a hollow cylinder or core fabricated from any suitable metal, such as aluminum, anodized aluminum, steel, nickel, copper, and the like, having heating element 36 disposed in the hollow portion thereof which is coextensive with the cylinder. Backup or pressure roll 28 cooperates with fuser roll 26 to form a nip or contact arc 38 through which a copy paper or other substrate 40 passes such that toner images 42 thereon contact elastomer surface 32 of fuser roll 26. As shown in FIG. 2, backup roll 28 has rigid core 44, e.g., a steel core, with elastomeric surface or layer 46 thereon. Sump 48 contains polymeric release agent 50 which may be a solid or liquid at room temperature, but it is a fluid at operating temperatures.
In the embodiment shown in FIG. 2, polymeric release agent 50 is applied to elastomer surface 32 via two release agent delivery rolls 52 and 54 rotatably mounted in the direction indicated. Thus, delivery rolls 52 and 54 are provided to transport release agent 50 to elastomer surface 32. Delivery roll 52 is partly immersed in sump 48 and transports on its surface release agent 50 from sump 48 to delivery roll 54. By using metering blade 56, a layer of polymeric release fluid 50 can be applied initially to delivery roll 54 and subsequently to elastomer 32 in controlled thickness ranging from submicrometer thickness to thickness of several micrometers of release fluid 50. Although the foregoing apparatus is described as including a fuser roller 26, it should be appreciated that the apparatus may include a fuser belt or the like, and such rollers and/or belts include coatings of a variety of types as described infra.
A key issue in various solution or dispersion coating operations, such as the coating deposited on a fuser substrate, is achieving a fine edge detail or border in a finished product. In some products or articles, such as fuser belts composed of flexible substrates, the edge of the finished product can be trimmed. In cases where this is not possible, or where precise coating composition control is desired, a suitable method of directing solution delivery has heretofore been unavailable.
Current methods of belt fabrication, such as belts used in printing systems, involve flow coating of a solvated polymer dispersion which includes a polymer, a crosslinker, filler(s) and optionally other flow agents, surfactants or co-solvents. For example, the base layer may be a silicone polymer. The coating is deposited on a belt substrate arranged on a rotating cylinder or offset cylinder and then kept at a controlled environmental condition, either ambient or within a rotation oven until most of the solvents are evaporated. The belt is then introduced to a higher temperature oven until the coating is crosslinked and any residual solvents or materials are removed. Alternatively, a secondary or tertiary layer is coated upon the substrate, i.e., base layer of the belt, to form a multi-layered article. For example, a release layer may be deposited as a secondary layer.
For fusing components, uniform compression is required for optimal fusing. Current methods of coating result in the area toward the edges where the material ends on the substrate to be much thinner in comparison to the body of the belt. Known coating methods result in the liquid material slowly dropping off and extending past the area which needs to be coated. To try and maximize uniform thickness through the body of the belt, the coating often extends past the desired coating area and then past the maximum width of the belt. Such a layer then cannot be encapsulated in an exterior coating layer, thereby leaving the ends of the substrate exposed which results in oil penetration of the under layer, de-bonding, offset and other early failure modes during the use of the belt. For example, the silicone substrate swells due to exposure to fuser oil thereby causing adhesion issues between the belt and the silicone. Moreover, such swelling may cause the release layer to detach from the silicone substrate. Merely extending the length of the belt is not possible due to hardware constraints.
The results of a known method of coating a belt are depicted in FIG. 3. The known method includes depositing silicone substrate 60 on belt 62. In this method, width 64 of silicone substrate 60 is less than width 66 of belt 62, e.g., the silicone substrate width may be 280 mm while the belt width is 300 mm. By leaving space on each side of silicone substrate 60, e.g., approximately 10 mm on each side, top coating 68, e.g., a release layer, may be deposited thereby encapsulating silicone substrate 60 and providing a barrier against fuser oil exposure, e.g., exposure to a release agent.
It has been found that the use of liquid coatings can result in a variety of problems. For example, when a liquid layer coats a surface, its ends gradually taper off due to surface tension, e.g., ends 70. Such taping precludes the necessary thickness of silicone at the required widths. If the layer is formed having an increased width to provide its required width, sufficient length at the edges is not present for proper encapsulation. For example, if length 72 becomes too small, top coating 68 will not be capable of encapsulating substrate 60. Moreover, in some instances, not only do tapered ends 70 form, but adjacent high points 74 also form. It has been found that the combination of a bump and adjacent tapered portion may comprise as much as 35-36 mm in width. Various methods have been attempted to remove the bumps or raised portions, e.g., using a sanding belt, and such attempts have heretofore failed to properly and effectively remove those portions.
The present disclosure addresses a system and method for applying a coating to a belt wherein the thickness of the coating is maintained across its full width while providing sufficient lengths of uncoated areas on the belt edges to permit full encapsulation thereof by an overcoat layer.